1. Field of the Invention
The present invention relates to a pole tip structure for a thin film magnetic head, and more particularly, to a horizontal thin film magnetic head which has well aligned pole tips.
2. Description of the Related Art
A horizontal thin film magnetic head differs from the typical pancake type thin film magnetic head in several respects. In the horizontal thin film magnetic head, the thickness of the pole tip layers establish the track pitch of the head, whereas in the pancake type head the track pitch is established by trimming the widths of the pole tip layers. Further, the horizontal thin film magnetic head is mounted on a sidewall of a slider whereas the pancake type head is mounted on a trailing edge of a slider. Accordingly, the direction of movement of magnetic media below the horizontal magnetic head is generally parallel to the planes of the thin films of the horizontal head whereas the direction of movement of the magnetic media with respect to the pancake type head is generally perpendicular to the planes of the thin films of the pancake type head. A distinct advantage of the horizontal thin film magnetic head over the pancake type thin film magnetic head is that a plurality of horizontal thin film magnetic heads can be combined to write closely packed tracks for high density multitrack recording, such as high definition television (HDTV).
The method of making the horizontal thin film magnetic head is somewhat different from the method of making the pancake type thin film magnetic head. With the horizontal head, the thin films for the pole tips PT1 and PT2 are deposited generally in a common plane with an insulating gap therebetween. As stated above, the track pitch is determined by the thickness of the pole tip thin films. With the pancake type head, thin films are deposited in sequence, one on top of the other, the first thin film being the pole tip PT1, the next thin film being the insulative gap G and the third thin film being the pole tip PT2. These thin film layers are then trimmed in the pole tip region for defining the widths of the pole tips to establish the track pitch of the head. An advantage of making a horizontal thin film magnetic head is that pole tip trimming is not required in order to define the track pitch of the head.
Several prior art methods have been employed for constructing the horizontal thin film magnetic head. The first method has been to construct the gap, which in a horizontal head is referred to as a sidegap. The pole tips PT1 and PT2 are then deposited on each side of the gap. A serious problem with this method is maintaining the mechanical integrity of the gap while it is freestanding as a pillar before plating the pole pieces PT1 and PT2. It is desirable to keep the length of the gap as small as practical to increase linear density (bit density) of the head. For example, if the length of the gap is 2000 angstroms and the height of the freestanding gap is 4 .mu.m-5 .mu.m to accommodate the pole pieces, it is unlikely that the freestanding gap will remain in place until the pole pieces are plated. The other prior art method frame plates the first pole piece, forms a gap layer and then sputter-deposits the second pole piece. With this method, the sputtered second pole piece presents a high topography on top of the first pole piece which must be removed by some method, such as lapping. Planarization by lapping is difficult to control. Further, lapping is not workable when the pole pieces are in a sunken location with respect to the substrate. The aforementioned fabrication problems associated with horizontal thin film magnetic heads apply equally as well to ring-type thin film magnetic heads shown in FIGS. 28a and 28b.